SOUTH PORTLAND, ME – Wright Express (WEX) has released its fuel prices outlook, with the company noting that the national retail gasoline average starts August at $3.57 per gallon, more than 25 cents per gallon higher than where it started in July.

States in the Midwest, including Indiana, Michigan, Ohio and Illinois, have seen prices increase nearly 60 cents per gallon during the past 30 days. WEX attributed this increase to higher crude oil costs and refinery issues squeezing fuel supplies. Diesel prices nationally are up to nearly $3.80 per gallon, which is the highest level since June 14.

WEX also reported that wholesale prices are increasing rapidly, at nearly $3.50 per gallon as of August 6. If these prices hold, retail gasoline prices would push past $4 per gallon in many states. WEX reported that experts believe the current runup in prices won’t last, though, with the price trend for 2012 looking similar to that of 2011. WEX reported that wholesale diesel prices are rising as well, but not at the same rapid pace as that of gasoline.

For fleet managers, after Sept. 15, the U.S. will be able to switch back to the easier to make, more plentiful winter grade of gasoline. WEX reported experts forecast “substantially lower” prices in the fourth quarter.